Hybrid system for control and monitoring of an amplifier

Abstract

A hybrid system (18) for control and monitoring of an amplifier (330) is provided. The hybrid control system (18) includes an analog control subsystem (81) and a digital control subsystem (82). The analog control system provides an automatic gain control loop for maintaining the gain of amplifier (330) at a predetermined level. The digital control subsystem (82) monitors a plurality of operating characteristics of amplifier (330) and commands the analog control subsystem (81) to reduce the gain of amplifier (330) responsive to certain predetermined fault conditions. The digital control subsystem (82) shuts down amplifier (330) responsive to other predetermined fault conditions. The digital control subsystem (82) also controls the power-on sequence and power-down sequence for amplifier (330), insuring that the gate bias voltage is first applied or maintained before the drain voltage is applied or removed.

What is claimed is: 
     
       1. A hybrid system for control and monitoring of an amplifier, comprising: an amplifier having an amplification input, a gain control input and an amplified output, said amplifier having a gain value varied responsive to a gain control signal input to said gain control input;   analog control means having (a) a first input coupled to said amplification input for sensing an input signal amplitude, (b) a second input coupled to said amplified output for sensing an output signal amplitude, and (c) an output coupled to said gain control input of said amplifier for maintaining a predetermined gain of said amplifier, said analog control means generating said gain control signal as a function of a measured gain value relative to a reference gain value;   monitoring means coupled to said amplifier for detecting at least one fault condition thereof and output of a "digital" signal responsive thereto; and,   "digital" control means having at least one input coupled to said monitoring means and a gain change output coupled to a third input of said analog control means for changing said reference gain value responsive to said at least one fault condition.   
     
     
       2. The hybrid system as recited in claim 1 where said amplifier includes a plurality of transistors coupled in parallel relationship, said digital control means outputting a signal at said gain change output for reducing said reference gain value by a predetermined increment responsive to a failure of one of said plurality of transistors. 
     
     
       3. The hybrid system as recited in claim 2 where said predetermined increment is approximately 3.0 db. 
     
     
       4. The hybrid system as recited in claim 2 where said digital control means includes an enablment control output coupled to an enabling input of said analog control means, said analog control means maintaining a minimal gain of said amplifier responsive to a disable signal input to said enabling input, said digital control means outputting said disable signal responsive to a failure of at least two of said plurality of transistors. 
     
     
       5. The hybrid system as recited in claim 2 where said monitoring means includes a temperature sensor coupled to said amplifier, said digital control means outputting said signal at said gain change output for reducing said reference gain value by said predetermined increment responsive to a temperature sensed by said temperature sensor exceeding a predetermined temperature value. 
     
     
       6. The hybrid system as recited in claim 1 where said digital control means includes an enablement control output coupled to an enabling input of said analog control means, said analog control means maintaining a minimal gain of said amplifier responsive to a disable signal input to said enabling input. 
     
     
       7. The hybrid system as recited in claim 6 where said monitoring means includes means for monitoring said output signal amplitude, said output signal amplitude monitoring means including at least one output coupled to an input of said digital control means for output of a signal to said digital control means representing a fault condition of said analog control means when said output signal amplitude exceeds predetermined limits, said digital control means outputting said disable signal responsive to said fault condition of said analog control means. 
     
     
       8. The hybrid system as recited in claim 7 where said monitoring means includes means for monitoring a reflected signal amplitude at said amplified output of said amplifier, said reflected signal amplitude monitoring means including at least one output coupled to an input of said digital control means for output of a signal to said digital control means representing a fault condition defined by a voltage standing wave ratio in excess of a predetermined limit, said digital control means outputting said disable signal responsive to said fault condition signal. 
     
     
       9. The hybrid system as recited in claim 4 further comprising a power source, said power source providing a gate voltage supply coupled to respective gate elements of said plurality of transistors and a drain voltage supply coupled to respective source elements of said plurality of transistors, said monitoring means including means for monitoring a gate voltage of said gate voltage supply and output of a signal responsive thereto, said digital control means outputting said disable signal responsive to said monitored gate voltage exceeding predetermined first limits. 
     
     
       10. The hybrid system as recited in claim 9 where said monitoring means includes means for monitoring a drain voltage of said drain voltage supply and output of a signal responsive thereto, said digital control means outputting said disable signal responsive to said monitored drain voltage exceeding predetermined second limits. 
     
     
       11. The hybrid system as recited in claim 1 where said digital control means includes a digital data output for communicating said at least one fault condition to an external control system. 
     
     
       12. A hybrid system for control and monitoring of an amplifier, comprising: a power source, said power source providing a gate voltage supply, a drain voltage supply and a voltage reference;   an amplifier coupled to said power source and having an amplification input, a gain control input, and an amplified output, said amplifier having a gain value varied responsive to a gain control signal input to said gain control input, said amplifier including a plurality of transistors, each of said plurality of transistors having a gate element coupled to said gate voltage supply, a drain element coupled to said drain voltage supply and a source element coupled to said voltage reference;   switching means coupled between said drain voltage supply and said drain element of each of said plurality of transistors for coupling said drain voltage supply to said drain elements responsive to a switching control signal coupled to a switching control input of said switching means;   analog control means having (a) a first input coupled to said amplification input for sensing an input signal amplitude, (b) a second input coupled to said amplified output for sensing an output signal amplitude, (c) an enabling input, and (d) an output coupled to said gain control input of said amplifier for maintaining a predetermined gain of said amplifier, said analog control means generating said gain control signal as a function of a measured gain value relative to a reference gain value and an enable signal input to said enabling input, said analog control means maintaining a minimal gain of said amplifier responsive to a disable signal input to said enabling input;   monitoring means coupled to said amplifier for detecting a gate voltage of said gate voltage supply and output of a first digital signal responsive thereto, said monitoring means detecting a drain voltage of said drain voltage supply and outputting a second digital signal responsive thereto; and,   digital control means having a plurality of inputs coupled to said monitoring means and a first output coupled to said enabling input of said analog control means and a second output coupled to said switching control input of said switching means, said digital control means outputting said switching control signal at said second output responsive to detection of said gate voltage and then in sequence changing an output at said first output of said digital control means from a disable signal to an enable signal responsive to detection of said drain voltage.   
     
     
       13. The hybrid system as recited in claim 12 where at least a portion of said plurality of transistors are coupled in parallel relationship, said digital control means outputting a signal at said gain change output for reducing said reference gain value by a predetermined increment responsive to a failure of one of said parallel coupled transistors. 
     
     
       14. The hybrid system as recited in claim 13 where said predetermined increment is approximately 3.0 db. 
     
     
       15. The hybrid system as recited in claim 12 where said monitoring means includes means for monitoring said output signal amplitude, said output signal amplitude monitoring means including at least one output coupled to one of said plurality of inputs of said digital control means for output of a signal to said digital control means representing a fault condition of said analog control means when said output signal amplitude exceeds predetermined limits, said digital control means outputting said disable signal responsive to said fault condition of said analog control means. 
     
     
       16. The hybrid system as recited in claim 15 where said monitoring means includes means for monitoring a reflected signal amplitude at said amplified output of said amplifier, said reflected signal amplitude monitoring means including at least one output coupled to one of said plurality of inputs of said digital control means for output of a signal to said digital control means representing a fault condition defined by a voltage standing wave ratio in excess of a predetermined limit, said digital control means outputting said disable signal responsive to said fault condition signal. 
     
     
       17. The hybrid system as recited in claim 16 where said digital control means includes a digital data output for communicating fault conditions to an external control system. 
     
     
       18. The hybrid system as recited in claim 12 where at least a portion of said plurality of transistors are silicon carbide transistors. 
     
     
       19. The hybrid system as recited in claim 12 where said amplifier includes a variable attenuator coupled to said amplification input and said gain control input, said variable attenuator being controlled to attenuate an input signal amplitude input to said amplification input responsive to said gain control signal input to said gain control input. 
     
     
       20. The hybrid system as recited in claim 19 where said analog control means outputs a gain control signal to drive said variable attenuator to substantially a maximum value responsive to output of said disable signal by said digital control means. 
     
     
       21. A power amplifier and control module, comprising: an amplifier including a plurality of silicon carbide transistors coupled between an input and output thereof, said amplifier including means for varying a gain value thereof responsive to an analog signal input to a gain control input;   analog control means having a pair of sensing inputs respectively coupled to said input and output of said amplifier and having an output coupled to said gain control input, said analog control means generating said gain control signal as a function of a measured gain value relative to a reference gain value; and,   digital control means having a plurality of inputs coupled to said amplifier for monitoring predetermined operating characteristics thereof, said digital control means having an output coupled to said analog control means for commanding said analog control means to vary said gain value to a predetermined value responsive to one or more of said predetermined operating characteristics exceeding predetermined limits therefor.